PH26543A - Soap composition - Google Patents

Description

The present invention relates to toilet soap ' compositions, partionlarly ecsp compositions in the form of tollet bars.

Toilet soap compositions in bar form typically contain 85 to 92% by weight of soaps and 8 to 15% by weight of water. The soap ie usually derived from blende of oile and/or fatty acide with a blend iodine value of not more than 60, and the poesibilities for incorporating filler materials are limited.

There are a number of constrainte which compel the adoption of such a composition. Notably, a greater water content or the preeence of more unsaturation, indicated by a higher icdine value, leade to a composition which is soft and sticky and cannot be processed into bars except with difficulty.

Conventional extrusion equipment cannot handle such soft and sticky compositions while running at normal : speeds. Increaging the water content of soap bare has the additional consequence that the bars tend to shrink on storage, leading to strese cracking. . Use of soluble fillers e.g. polyols tends to produce deterioration in properties perceived by the - user, such ag lather formation, bar hardness, rate of wear and development of surface mush,

To summarize, a successful toilet bar composition

. needs ideally to be capable of processing on conven- tional extrusion equipment (so the composition must not be too soft and sticky), must provide satisfactory - lather and other user-perceived properties and must avold cracking. A further pitfall which a soar composition must avold le efflorescence, that ie to say crystalline growth appearing on the surface of bare during processing, storage or use,

There have been a number of proposals to incor- porate inorganic electrolytes into soap bare in vary- ing amounts and for various reasons. See for example

GB 1244346 (Colgate).

We have now found that the incorporation of one particular electrolyte makee 1t possible to avoid the constraints referred to above, while still maintaining satisfactory properties. By contrast we have found that thie is not possible with other electrolytes we have tested.

According to a firet aspect of the present invention there ie provided a toilet soap bar on comprieing: : 40 to 89% by weight soap (reckoned as anhydrous) 1 to 33% by weight tetrasodiumpyrophosphate (reckoned as anhydrous Na, P,0., and {x + 4)% to (x +19) % by weight water, where x% is the calculated amount of water required to effect complete hydration of the pyrophosphate to its decahydrate, i - 3 =

Hydration of eodulm pyrophosphate to ite decahy- drate proceeds by the reaction

Na, P,0; + 10 Hy0 — 5 Na, P,0,.100,0

The value if x can readily be calculated from the amount of pyrophosphate. The molecular weight of anhydrous Ba ,P,0, is 266. The molecular weight of water is 18. So, if the percentage by weight of anhydroug pyrorhoephate is y %, the percentage of water is given by:

X% = v% x 18 x 10 = 0.68y% 266 :

In other words the amount of water ie given by (0.68y + 4) % & X% & (0.68y + 19%) where x% ie the total amount of ‘water by weight and y¥% ie the amount of sodium pyrophosphate reckoned as anhydroue.

By including eodium pyrophosphate we have found that it is possible to lower the amount of soap in the . compogition to lie in the range from 40 to 89% by weight (reckoned as anhydrous) with a water content lying between 4.68 and 41.44%, while still retaining acceptable yield strese (i.e hardness) and also keeping other properties satisfactory. The amount of soap : (reckoned as anhydrous) in the composition need be not more than 85%, or even not more than 80% by weight (reckoned as anhydrous soap). The level of sodium pyrophosphate preferably lies in a range from 10 to 30%

t . by weight. The actual proportion of ingredients selected in any one case will depend among other thinge on the desired properties of the finished bar and on for example the type of goap blend selected for inclusion in the bar. We have found for instance that less water ie needed with soft oil blende than with hard cil blends (ie. IV < 60) for which a minimum total water content is preferably 8.68 wt¥,

The hardness of a goap bar can be quantified by measuring the yield stress of the bar. Toilet soap bars embodying the preeent invention have a yield stress at 20°C of at least 3.0 x 10° Nm 2, up to a preferred maximum yield stress value at, 20°C of 10 x 10° Fm 2. Measurement of yield stress ie described inter alia in Elementary Rheclogy by G W Scott Blair, ’ Academic Press, London 1868 and Rheometry: Industrial

Applicatione Ed. K. Waltere Research Studies Press (a division of John Wiley & Sone Ltd.) New York 1880. : . Soap sources suitable for use in the present compo- sition include conventional tollet eoap sources such as tallow, hydrogenated tallow, hydrogenated rice bran oil, hydrogenated linseed oil, palm oll, hydrogenated palm oil, coconut oil and babaeeu cil in the usual ecap blend proportions of 60 to 85 wt% tallow, hydrogenated tallow, hydrogenated rice bran oil, hydrogenated lin- seed oil, palm oil, hydrogenated palm cil, the like and mixtures thereof and 40 to § wt% coconut oil, babassu t oil, the like and mixtures thereof. We have however found that it is posgible to use in compositions embodying the present invention cil blends whose fatty acid moieties have a degree of olefinic unsaturation that is higher than usually used for a tellet soap bar. In particular we have found that the present composition permits the use of soap blends having an iodine value of more than 60. Examples of cile that Co can be employed containing a high degree of olefinic unsaturation include soyabean oil, sunflower oil, linseed oil, cottonseed oil and rice bran oil. The proportion of such oils present can ‘be up to 100 wt% of the soap blend and can for instance be determined by the prevailing price of locally available materiale.

The soap bar could thus be made from a soap blend having an lodine value of up to 130. All the scape present are preferably sodium scape.

The present compositions permit the inclusion more water soluble filler than would be possible in the abgence of sodium pyrophoephate. Examples of such water soluble fillers include sugars, glycerol, sorbitol and sucrose. The amount that it is possible > to include will vary from filler to filler. In the case of sucrose it ie poseible to include between 0 and 10 wt% with respect to the final weight of the bar, without adversely effecting bar properties to an unacceptable degree. 1t is possible to render the present compositions t superfatted ie. to ensure the presence of free fatty acide in the bar either by adding the deeired free fatty acide per se to the scap blend or by adding an acid such as citric acld or rhosphoric acid to the soap

A blend which displaces free fatty acid from the goar mixture. Suitably the compositione can be guperfatted so as to ensure the presence of 5 to 10 wt% free fatty acid with respect to the soap blend employed.

There are other salte beside sodium pyrorhosphate which will take up water as water of crystallization.

We have found however that none of these ealte we have otherwise tested 1s suitable. In some cases the temperature at which the water of hydration is lost le relatively low, so as to be below the amblent temperature in hot climates. Additionally with all conventional hydratable ealts except sodium pyrophos- phate, we have obeerved efflorescence. Although we do not wish to be bound by any theory it would appear that the water solubility of an electrolyte determines whether efflorescence will occur from compositicone which have amounts of soap and water in accordance with the present composition. There appears to be a rather : low limit on water solubility, above which effloree- cence is observed. Only tetrasodium pyrophosphate comes below this limit and hence provides a soap bar avolding problems of efflorescence.

Compositions embodying the invention can be produced by mixing sodiam pyrophosphate with moilstnre-containing eosp. A preferred techniane le to add snhydrous sodinm pyrophoephate to so-called neat soap containing spproximately 70% sosp and 30% water with the nest eosp in x molten state. The eodiam pyrophosphate can be ndded ss a dry powder, &6 2 hot concentrated solution or as a selarry with = emznll amount of hot water. The sosp mixture containing sodium pyrophosphate cmn then be dried to ite intended water content, optionally by use of mn vacuum flash dryer ae ie conventionally need for drying nest cosp to the water content spproprisbe for conventional tollet goap. However, less drying will be required for the preeent compositions. An mlternmtive processing route 156 would be to meter the sodium pyrophosphate into the flow of neat soap as it goes to the dryer.

Another production route wonld be Lo mix the godinm pyrophoephate with somp which hae been oblained by drying neat sosp, e.g. soap noodles coming from a vaommm flash dryer. HWixing with such 6oRp noodles ann be ocmrried out with = mixer which applies shemnr to the . mixture.

By adding the sodium pyrophosphate at a relatively early stage in the processing of the soap into bars, the sodium pyrophosphate introduced into the compos i- tion reaches ite hydrated state at an early etage, giving a composition which can be subjected to . -g = in '

conventional subsequent proceesing steps. Normally euch steps includes admixing of minor ingrediente such ae dyes, perfumes, antioxidante, preservatives, e.g. with a chip mixer, milling, plodding, extruding and b stamping into bars.

In a second aspect therefore the present invention ar, provides a process for preparing a soap composition according to the first aepect of the present invention, comprising admixing tetrascdiumpyrophcsphate at a level of 1 to 33 wt% calculated with respect to the final toilet soap bar composition with molsture containing soap.

Suitably the moisture containing scap has a water content in excees of 20 wt% and the eoap ie subjected to a drying step. Conveniently the molieture containing soap 1s neat soap.

Generally the resulting composition will then be milled, plodded and shaped into bare.

The present invention will now be described further and exemplified by the following Examples in which all percentages are by weight.

Example 1

A number of bars were prepared with varying contents of soap, water and tetrasodium pyrophosphate.

The bars were prepared on a pilot plant, adding tetrasodium pyrophosphate in the form of a slurry to neat soap (approximately 30 % wt water content) =f =

. thereafter drying to the desired water content, milling, rlodding and stamping into bars. The pyrophosphate slurries were freshly made using an amount of water calculated to be 6% by weight of the b final composition. The neat soap Wag Aa conventional 80/20 tallow/coconut 80AP.

The yield stress of the bare ab 20°C was determined by observation of the extent to which a bar wee cul by 2 weighted cheese wire daring = specified time. A horizontally braced cheese wire of dimsmeter d em enbpended from & connterbalanced and freely pivotable nrm WAS brought into contact with = freshly prepared bar of soap cooled to room tLemperatnre (20°C).

A corner edge of the 605P wae positioned under the wire guch that when = weight W gm Was placed on the Arm directly sbove the cheese wire, the length of ent L cm made by the wire increhsed to the limit where the stress exerted by the wire equals the resistence of the bar. The stress exerted by the wire at this limit is

Lo 20 equal to the yield stress of the goap bar. The time

E taken to reach thie limit wae of the order of 30 seconds. In practice a standard 1 mimate cnt Lime was allowed in esch CRBS.

For a bar having an orthogonal corner edge in tranverse Cross section the yield stress of the bar was calculated using the following formula:

«

Yield stress = 3 x H88.1 Mu 2 8 L 4

The in-uee properties of the bare, specifically rate of wesr, mash formetion during nee snd lather generation, were tested using bare which had been stored at room temperature of 20°C for at lesmst four weeks and examined for A

Bare were stored ander accelerated ageing conditions mand examined at intervals. The storage conditions comprised storing for one week ab 20°C with 90% relstive humidity then for one week a1 37°C with 70% relative humidity and repeating thie cycle for several monthe while examining the xppesarasnce of the bare each week.

The various compositions and their yield streee values are set out in the following Table 1 where the term “free water (theory}" signiflee the amount of water calculated to remain after full hydration of the pyrorhosphate. In the table the control composition ise " 20 a conventional 80/20 tallow/cocénut soap bar composi- - tion without sodium pyrophosphate.

TABLE 1

SAMFLE % SOAP % Ha, Pp0, % WATER ¥% FREE YIELD STRESS (anhy.) (anhy.) WATER at 20°C (theory) (m2)

Control 88 0 12 12 4.0 x 10°

Al 78 4 18 15.3 3.0 x 10°

A 50 15 25 14.8 3.9 x 10°

B 56 15 29 18.8 3.5 x 10° c 55 15 30 19.8 2.5 x 10°

D 53 15 32 21.8 1.2 x 10°

E 56 20 24 10.6 7.5 x 10°

F 50 20 30 16.5 3.1 x 10° g 45 20 35 21.5 1.0 x 10°

H 40 20 40 26.5 0.6 x 10°

I 45 36 19 5.4 21.8 x 10°

J 45 15 an 29.8 0.2 x 10°

K a4 26 30 12.4 6.1 x 10°

L 33 33 34 11.6 4.8 x 10°

The compositions in Table 1 embodying the present invention were sll observed to have an yield etrese 29 grexter then 3.0 Xx 10° nom. 2, which ie the minimom hardness for m composition cmpable of processing into toilet bare neing conventlonal equipment.

By contraet the comparative compositions Cc, Db, @,

H and J with a theoretical free water content grenter than that permitted by the present invention had inenfficient hardness.

Compoeition I had insufficient water to achleve a full hydration of the pyrophosphate, giving a negative theoretical value for free water. The resulting composition was found to be extremely hard and ite in-use properties were poor, that ie to say it had =a low rate of wear and low lather formation. It wae also obeerved to give efflorescence during etorage. i Composition L had insufficient soap to meet the requirements of the present invention. Its hardness was satisfactory but ite in-use properties were pooy.

The in-use properties of the compositions which did lie . within the requirements of thie invention were in every case found to be gatisfactory.

Measurements of the rate of wear, mush and lather characterietice of bars control, Ai, A, F, RK and L were made and the results are given in Table 2 below.

SAMPLE RATE OF IN USE LATHER

WEAR MUGH (mle) ny

Control 23 : 6 41

Al 28 13 46

A 21 6.5 35

F 22 12 35

K 17 4 34

L 18 5 29 ee

The resulte in Table 2 show that bars embodying the present invention have comparable properties to the control bar having a higher soap content and containing no scdium pyrophosphate ol

Example 2

A number of bare were made in the same manner As . for Example 1 but in place of tetragodium pyrorhoerhate other hydratable ealts were employed. The bars were gtored under accelerated ageing conditions and Lo appearance of the bars was noted 4b iitervalé: The : . compoeliticne and the results of the storeae tests are get out in Table 3 below: as noted in the table all the bars gave an unsatisfactory appearhnce iith efflo- mn rescence apparent at some stage. So

Table 3 So

ELECTROLYTE ¥ SOAP ¥ RLECTROL FREE WATER RESULT (anhy.) (anh) (theory)

Sodium sulphate 78 3.9 13.2 E,C,PE

Sodium carbonate 18 3.9 ii.5 E.C

Sodinm metaborate 78 3.8 138 IRE

Trigodine orbho- 59.2 12.0 13.0 E phoephate | | i

Disodium hydrogen 61.8 10.4 dzi0 E orthophosphate oo ‘ol ; Copa . Ci . CL Ch Cn oo a . a ETE

: E = efflorescence, IE = efflorescence in use,

C = cracking, PE = efflorescence during processing

Example 3

Bars were made in the same manner as for Example 1, with varying amounts of &ucrcse incorporated with the tetrasodium pyrophosphate. Yield strees of the bars was measured at 20°C. In-use properties were obgerved, neing bare which had been stored at 20°C for at lesst four weeks. The in-use property of meh 190 formation wae memsured by mesne of xn Ltesd conelsting of weighing the smount of waeh ecraped from = bar which hae been mllowed to eband in = epecified depth of water for » specified time.

The compositions and results are set out in Table 4. !

SAMPLE SOAP Na ,P,0; WATER SUCROSE YIELD "IN-USE ’ wt% wt% wt wi STRESS MUSH a :

Comtrll BB n 140 0 an=x10® 9.0

Cntrl2 0 0 30.0 op 1.6 x 10° 17.0

M 83 n 27.0 © 10 2.2 x 10° 30.0 h 54.5 15 25.5 5 3.9 x 10° 12.4

P 50.5 15 - 24.5 10 2.8 x 10% 17.0

‘

In the teble the fired control 16 a conventional gh/20 tmllow/coconnt toilet sopp composition. The pecond conhrol ie neat s03D, which had mich lower hardness znd higher meh deve lopment, . Comparative composition M shows that addition of NR without tetrasodinm pyrophoepate glvee BI inndeannte improve- ment in hardness snd excessive wmeh format lon.

Composition H which tneindes vehrasodinm pyrophosphate hae estisgfmnctory hardness and mach lege meh formation.

Composition FP with a grester level of edcrose and with retrasodinm pyrophosphate hae satisfactory hatdness.

A number of bars were made in the game manner Ae for Example 1, but employing blends of oils for the soap base which have an jodine value of hore than 60.

Two different oil blends were used. In oné (@) the mixture wae a blend of 32 wt¥ tallow, ig wx soybean oil and 20 wt coconut oil having an overall fotine value of 83. In the ober blend (R) a mixture of 80 wt nn % soyabean oil and 20 wt% cocomit oil wag employed having an overall todine value of 10. thé compos i- . tional make-up of the bare and the yield stiese value measured at 20°C for each. type of bar ie given in

Table 5 below. : Co EE

Lo ) RE _

Co Ah co

Po Co Cee Co

Lo Cs

‘

SAMPLE SOAP SopiuM WATER YIELD STRESS (wh%) PYROPHOS- (wh) (m2)

PHATE

(wt%)

Q 58 20 22 3.4 x 10°

R 54 25 | C21 3.9 x 10°

In each case the bare had a vield etreks of more to than 3 x 10° m2 and thus provided toilet bare of 1D acceptable hardnese. Comparative bars containing eoaps from the same oll blends bitt with ro added tetrascdium : pyrophosphate were extremely soft and sticky and : imposeible to process into bare on conventional extrusion equipment. Bar Q had the following in-use properties: rate of wear 17%, in Gs mush B and iather oo volume 36 mle, which characterietice are comparable to

CL those of the control bar employed ih Example 1. . A number of bars were ade 1h ‘the game manhér as Ll : a0 for Example 1. The present bars Webd made howdver from a 60/40 blend of tallow and coconiit Boape wiidch kab oo pi, guperfatted ie. contained fiee patty sclds (FFA). The Co J : | amount of free fatty acid present ie expressed as a percentage of the tallon/coconlit E6ap blend pregent ie. a 60/40, 5 blend means a blend of Boars compriging 60 : = 17 =

Co wt¥ tallow eosp and 40 wi¥ coconut oll eoap in which ie : additionally present 5 wid free fatty mcid with respect to the sosp blend.

The formulation detaile are given in Table 6 5b below.

Table 6

SAMPLE SOAP /FFA SOAP/FFA SODIUM WATER

CHARGE (wt%) PYROPHOS- = (wt¥)

PHATE

(wh%) oo - {anhydrous { : _ 8 60/40, & 51 iB 24 oo oo oo T ~ Bn/an; 1D 66 | is ~~ 19 . Ce . oh Cv ela Beye he ar ae

Control B0/40, 7 BB 0 Loz Co

For esch type of bar ite yield shreds at 20°C, : pate of wear, wash’ znd lather sharsctetishich were .. peeessed. The reealte are given in Table 7 below.

Table 7 ) "os | : . . EXAMPLE YIELD STRESS WEAR OBJECTIVE LATHER (n=?) © (%) Mus VOLUME

S sy x10® 20 7 41 - T 3.1 x 10° 18 5 66

Control 3.0 x 10° 17 1d. 53

‘

L

The results in Table 7 show that superfatted bare containing tetrasodium pyrorhosrhate have in uge and hardneee properties comparable to superfatted bars containing no pyrophosphate and hence correspondingly : 5 more of the soap/fat charge. : ‘ Coad di \ , CL od . i , i , ot [a Co

Claims (8)

CLAIMS :

1. Toilet soap bar comprising: 40 to 89% by welght soar (reckoned ae anhydrous) 1 to 33% by weight tetragodiumpyrophosphate {reckoned as anhydrous Na,P,07), and (x + 4) % to (x + 19) % by weight water, where x% ie the cal- culated amount of water required to effect complete hydration of the pyroephosphate to ite decahydrate, ” and is equivalent to 0.68 of the percentnge by welght of tetrasodiumpyrophosphate computed as 0.68 of 1 to 33% “thus giving a total water content in the bar lying between 4.68 wt% and 41.44%.

2. Toilet soap bar according to clalm 1 wherein the soap content (reckoned as anhydrous) 1s from 40 to 85 wt%.

3. Toilet soap bar according to claim 2? wherein the soap content (reckoned as anhydrous) is from 40 to 80 wt.

4. Toilet scap bar according to claim 1 wherein the level of tetrasodiumpyrorhosphate (reckoned ae anhydrous) lies in a range from 10 to 30% by weight with respect to the final toilet soap bar compoeition.

5. Téilet soap bar according to claim 1 wherein the soap compriges a blend of soaps whose fatty acid moleties have an iodine value in the range from 60 to oo

130.

6. Toilet soap bar according to claim 1 wherein the bar contains free fatty acide within the range 5 to wt% with respect to the soap blend employed.

7. Tollet soap bar according to claim 1 wherein the bar contains a water soluble filler.

8, Toilet soap bar according to cldim 1 having a : yield stress at 20°C lying within the range 3.0 x 10° 10 tn 2 to 10 x 10° N72. oe Ce ein : ; ? Piso ie ee tri 3 a as pb tea mR : Co © JOHN GEORGE CHAMBERS CAROLINE SUSAN CORDERY = NORMAN HALL oo MICHAEL HOOD a | oo "GEOFFREY iRLAM Inventoré = 21 = i